Posts tagged ‘marestail’

Strategies are Limited for Late Season Marestail Control in Soybeans

University of Illinois’ Aaron Hager wrote an excellent article on Late-Season Herbicide Applications in Soybean.  Many farmers are struggling with weeds such as volunteer corn, velvetleaf, etc.  Most of these weeds are easy enough to control but there are a couple of weeds that are very difficult to control. One of those weeds that is making its presence known in Ohio is marestail.

Unfortunately, there are not many great options for postemergence control of marestail. In populations that are not glyphosate- or ALS-resistant, postemergence application of glyphosate, FirstRate, or Classic can control small plants that emerge after soybean planting. A combination of glyphosate plus either Classic or FirstRate has the most chance for success, but primarily for control of plants that emerged after soybean planting and are still small. Postemergence application of Ignite in Liberty Link soybeans can control small plants.

Below is a factsheet from Purdue/OSU on marestail control; you’ll note the information is heavily geared to preplant/preemergence control.

View this document on Scribd

July 28, 2010 at 8:35 am

Tips and Suggestions for Controlling Marestail this Fall

The following is condensed from the October 6, 2009 OSU CORN newsletter written by Dr. Mark Loux on marestail control.

The goal of a marestail management program is to ensure that the combination of fall and spring burndown and residual herbicides results in a weed-free seedbed at the time of soybean emergence, and little to no emergence of marestail between soybean emergence and crop canopy closure. Even the most effective marestail management programs can fail to completely achieve this, but they often keep the populations low enough in the soybeans that they are not problematic.

Marestail plants that emerge in late summer or fall are easily controlled with a fall herbicide treatment. However, it’s essential to realize that a fall herbicide treatment is not likely to accomplish everything that’s needed in an effective marestail management program.

In those marestail-infested fields requiring a fall herbicide treatment for management of other winter annual annual weeds or dandelion, it is essential not to apply all of the residual herbicide in the fall. This also applies to those fields that are typically so wet that soybeans cannot be planted until mid to late May. In this situation, the goal of a fall residual herbicide treatment might be just to ensure that marestail are not too large when burndown herbicides are finally applied in May. Regardless of the type of herbicides applied in fall, an effective rate of a residual herbicide should still be applied in the spring, to maximize control of marestail that emerges in May and June. We suggest one of the following approaches [for marestail control]:

1. Apply a combination of glyphosate and 2,4-D in the fall, followed by application of residual herbicide in the spring prior to soybean emergence. At the time of soybean planting, the field is likely to be infested with marestail that emerged earlier in spring, so include effective burndown herbicides (2,4-D, Gramoxone, glyphosate, or Ignite or some combination as appropriate based on herbicide resistance, plant size and time until soybean planting) to control emerged plants.

2. Apply 2,4-D with Canopy DF or EX at fairly low rates (e.g. 1 oz of EX or 2 oz of DF) in the fall, followed by application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting). It is possible to follow the fall Canopy application with a spring application of a chlorimuron-containing herbicide, as long as the total does not exceed the maximum labeled rate of chlorimuron for the soil type.

3. In ALS-resistant populations where Canopy will fail to provide any residual control of marestail, it may be possible to substitute a combination of 2,4-D with metribuzin in the fall. This combination should control most emerged winter annuals, but can be weak on dandelion. Follow with application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting).

Full podcast here:

October 21, 2009 at 1:00 pm

Marestail Control in Soybeans

This article is devoted to one of the most problematic weeds in soybeans: marestail. Marestail is an upright growing plant and can reach 4 feet if not mowed or controlled. Marestail begins as a basal rosette similar to other winter annuals. Following the rosette stage, Marestail expereinces a stage of rapid vertical growth refered to as ‘bolting’. The leaves are 3 – 4 inches in length, and have widely toothed margings. And the stem of marestail is simple and unbranched, and covered with hair.

In a recent fall weed-scouting project, I noted marestail in nearly 20% of the soybean fields in Van Wert County. For those who are battling this weed already, you know that marestail is difficult to control. Marestail is diffiuclt to control for many reasons. First, marestail has the ability to germinate throughout the year. In fact, marestail is typically classified as both a winter annual and a summer annual because it can germinate in the fall and throughout the summer. Next, marestail is tolerant and in some cases resistant to glyphosate. So an application of glyphosate may have little to no effect on marestail. Last, marestail is a prolific seed producer. Weed scientists have reported seed production up to 200,000 seeds per marestail plant. Yes, that’s per single plant. The seeds are small (typically 2mm) and are dispersed easily by wind and equipment.

In OSU research, the most effective control of marestail in soybeans has occurred from a combination of 2,4-D ester, residual herbicides and either glyphosate or paraquat applied in April, when the marestail is still in the rosette stage or has only an inch or two of stem elongation. But even with this ‘loaded’ herbicide package, expect a few marestail escapes. If marestail populations are heavy, OSU researchers recommend delaying the herbicide application until very late-April or early-May to catch as many emerged marestail plants as possible.

Below is the full podcast on marestail.

November 5, 2008 at 7:00 am

End of Season Weed Survey

On Tuesday, September 23, 2008 I spent the better part of the day conducting a comprehensive weed survey in Van Wert County. Why, you ask, would I drive 180 miles within a one county area to look at weeds? The answer is simple: to better serve my local clientele’s needs. By knowing what weeds are problematic to area farmers, I can better plan winter meetings, etc. At the end of the day, I scouted 80 randomly selected soybean fields. This project is actually part of a larger project in Ohio, and I am just one participant. I sent my data to Mark Loux for his assessment, but I thought I’d share with you my results.

I surveyed summer annual weeds only, and did not look for winter annual weeds. Also, I limited my survey to soybean fields only.  Basically, this saved time for me; by looking only for summer annuals in soybean fields I did not have to walk into a field and I could make my observations from the edge of the field. Please note that my observations are qualitative and subject to my interpretation. I was asked to score the weed infestation on the following scale: 1=Occasional (A plant of the species as an occasional individual plant), 2=Large patches (A patch(s) of 8 or more plants of individual species scattered in field), or 3=Widespread (Numerous patches or individual plants of the species across the field).

Rankings (from most often to least often weed found in soybeans)

#1 Marestail- I found this weed in nearly 20% of the soybean fields I randomly selected. This weed has become prevelant in Van Wert County and is very difficult to control. This weed seems to be more abundant in southern Van Wert County. The average infestation was 1.8 (on a scale of 1-3, see above for explanation of scale).

#2 Volunteer corn – My guess is that I was seeing volunteer Roundup Ready corn, but I have no way of knowing that for sure. Average infestation of 1.1.

#3 Common ragweed – No surprise here. Common ragweed is found in nearly every soybean field, but is usually easily controlled by glyphosate. These escapes were probably due to a too early application of glyphosate. Average infestation of 1.7.

#4 Giant ragweed – Fortunately, this weed does not flourish throuhout Van Wert County and seems to be isolated to certain fields. Like Marestail, this weed ranks at the top of the list with regards to difficulty of control. Average infestation 1.0.

#5 Foxtail – I was surprised to see foxtail make it on the list. Foxtail is easily controlled by glyphosate and/or selective grass herbicides. Also, the infestation was high with an average score of 2.5.

#6 Lambsquarters – Lambsquarter becomes very difficult to control when the weather turns dry and hot, and that is exactly what happened during August. Average infestation of 1.0.

#7 Pigweed – I was also surprised to see pigweed on the list. It is not normally a weed that I’ll find in a field this late in the season. Usually this weed does well along field edges but not in the field. Average infestation 1.0.

There were other weeds I noted, but not in enough frequency or infestation to make the list. Velvetleaf, cocklebur and smartweed were noted in one or two soybean field edges. Bear in my that this survey is done for soybeans only (since soybean acres outnumber corn acres nearly 2:1 in Van Wert County). Had I stepped into some corn fields I probably would have found more velvetleaf and cocklebur. In my experience these weeds can become prevalent in corn fields in Van Wert County.

Let me know if you have a different observation or wish to augment my observations.

September 25, 2008 at 7:00 am


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